Ablation is often the recommended treatment for certain fibroids, tumors or other tissue masses. For example, local ablation may be carried out by inserting a therapeutic device into target tissue and carrying out a therapeutic activity designed to destroy the tissue's cells. In one case, electrical energy may be applied to the affected area by placing one or more electrodes into the target tissue and discharging electric current therefrom to ablate the tissue. Alternatively, fluids with appropriate properties may be injected into the vicinity to chemically necrose the target tissue.
When RF energy is used to ablate tissue, the size and shape of the region of tissue ablated depends in part on the configuration of the electrodes and on the strength of the RF charge imparted to the target tissue. The energy applied to the tissue dissipates very rapidly with distance from the electrodes. Thus it is difficult to maintain the high level of energy density required to sufficiently ablate tissue across a large tissue volume. Therefore, ablating large portions of tissue often necessitates multiple applications of the ablation electrodes at various locations within a target tissue mass. High conductivity electrodes have been employed to improve the efficiency of these procedure and low friction electrodes have been employed to facilitate insertion and removal of the electrodes.
The energy transferred from electrodes to tissue declines as tissue adjacent to the electrodes becomes desiccated and loses its conductivity. This desiccated tissue surrounding the electrodes acts as an insulator preventing RF energy from reaching tissue separated from the electrodes by this insulative, desiccated tissue. As the tissue becomes desiccated, it often sticks to the electrodes making repositioning of the electrodes more difficult and time consuming.